Each of U.S. Pat. Nos. 5,640,143; 5,986,357; 6,078,253; and 6,222,191 is hereby incorporated by reference.
1. Field of the Invention
The present invention relates generally to modular lamp controllers and more particularly to methods and apparatus for retrofitting a lamp for use with a modular lamp controller.
2. Background
Some HID lamps may be operated at reduced power. This can provide not only energy savings and reduce cooling expenses, but can also reduce power consumption during peak demand periods. Some lamp types are suitable light sources at both low and high power.
Conventional dimming systems for HID lamps have been available for many years. One scheme uses a ballast, two capacitors, a switch, and the HID lamp. Several ballast types and configurations may be used. The main requirement for conventional dimming systems is that the electrical inclusion and removal of an impedance in the ballast circuit will cause the lamp to burn at desired power levels.
Most lamp manufacturers have made recommendations about the operation of their lamps with dimming systems. Typically, they require that the lamps must be operated at full power for a minimum warm-up time before they are allowed to operate at lower power. The lamps must also not be operated below a minimum power.
A Constant Wattage Autotransformer (CWA) or constant wattage isolated (CWI) type ballast arrangement 100 is shown in FIG. 1 (prior art). If dotted line 101 is connected, this figure illustrates a CWA ballast. If it is not connected, the figure illustrates a CWI ballast. The magnetically coupled coils 102 represent the ballast. Element 103 is the AC supply to the fixture, and element 104 is an earth ground connection. Element 105 is the capacitor in the fixture. Element 106 is the lamp mogul, and element 107 is the lamp and/or lamp fixture, which may be an HID lamp.
FIG. 2 (prior art) shows the connections used for a conventional dimming system 200 using a series capacitor arrangement. FIG. 3 (prior art) shows the connections used for a conventional dimming system 300 using a parallel capacitor arrangement. In both arrangements, the switch 203 is used to include or remove a connection to one terminal of one of the capacitors in the circuit. The capacitor values for either series or parallel combination may be selected so that closing the switch operates the lamp at full power. When the switch is closed, the lamp is in series with a higher valued capacitance and operates at full power. When the switch is open, the capacitance is reduced, and the lamp drops to a lower power. Lumen output and color temperature completely changes for most lamps within a minute of a commutation of the switch.
To achieve a conventional dimming system, capacitor 105 of FIG. 1 has been replaced by capacitors 201 and 202 in FIG. 2. Capacitor 105 of FIG. 1 has been replaced by capacitors 301 and 302 in FIG. 3. Elements in the ballast circuit that are in series may be manipulated with reference to position and polarity without changing the performance. The threaded portion of the mogul base remains connected to an electrical potential close to neutral or earth ground for safety. The most likely connection points based on ease-of-wiring to real fixtures are shown as elements 204 and 205 of FIG. 2 and elements 303 and 304 of FIG. 3.
If the capacitance required for full power operation is 20 uF, and the capacitance required for low power is 15 uF, suitable values of 201, 202, 301, and 302 may be readily determined. In one example, they are 20, 60, 15, and 5 uF respectively. A series combination will require two larger value capacitors (20 and 60 uF) than a parallel combination (15 and 5 uF) for the same full power (20 uF) and low power (15 uF) combined values. This means that the series choice will most likely be physically larger than the parallel choice. For this reason, most conventional dimming systems utilize parallel combinations, when available.
The series combination has lower voltage across the switched capacitor and switch. In FIG. 2, the voltage from ballast to lamp is divided between capacitors 201 and 202 if switch 203 is open and across 201 when the switch is closed. In FIG. 3, the full voltage from ballast to lamp is applied to both capacitors 301 and 302 when the switch is closed.
Installing a conventional dimming system is normally accomplished by replacing the designed capacitor for a ballast with either two separate capacitors or a dual capacitor. Inconveniently, conventional systems require that the fixture be taken down and taken apart for installation.
In the configuration used with FIGS. 2 and 3, one controller may be used to control and power many switches, but there is no way for the controller to know how long specific controlled lamps have been warming up. If the lamp shuts-down for any reason, the controller may not run that lamp for a new warm-up. If control is not present at the lamp fixture, it may result in incorrect warm-up or no warm-up at all, which may damage lamp 107.
Any occupancy sensor (not shown) used with these conventional dimming systems is typically mounted separately from the switch and control. The occupancy sensor requires separate alignment and mounting, which may be very inconvenient and time consuming.
Troubleshooting of conventional systems is time consuming, problematic, and often requires that the lamp be taken down and taken apart.
One significant problem with conventional dimmer systems is that it is difficult to determine if a problem stems from the lamp, fixture, or system. Since the fixture must be taken apart for the installation, problems may be found anywhere from the lamp to the connection to the mains. Damage may occur to the lamp in handling during installation of the system. The only way to remove the switch and control from the system is to remove the wire connections to them. Isolating part of the system for testing is difficult without first taking the fixture apart.
In addition, components may be damaged during the troubleshooting period. If too large a capacitor is installed in series with the lamp, it could cause excessive heat and damage components. If parallel capacitors are reversed, it can cause the lamp to extinguish when switched to low power. This puts extra wear on the ignitor used with some lamps. If too small a capacitor is installed in series with the lamp, it may not allow the lamp to start at all. This puts extra wear on the ignitor and may damage the lamp electrodes over time.
If the control wiring is incorrect, every connected switch will be affected. Improper or missing warm-up will cause premature end-of-life and lower lumen output for the lamps. If there is an open in the circuit, the lamp will not ignite, but if an ignitor is used, it may run continuously. This will limit the life of the ignitor.
Further, with conventional systems, it is difficult to quickly see if a lamp is stuck in either high or low power if there is no simple way to change state. If a controller is present with the switch 203, it may not allow the lamp fixture to dim if it is in a warm-up period. Warm-up periods may range from a few minutes to half an hour depending on the lamp. This is a long time to wait before testing a system. If the switch 203 is independent at the lamp fixture 108, a control has to be wired to enable a test. There is no built-in mechanism to perform a simple test of conventional systems.
Troubleshooting is even more difficult when there are multiple lamp fixtures 108 connected to one occupancy sensor (not shown). Not only are there a larger number of connections per occupancy sensor, but also an occupancy sensor used to control many fixtures is more likely to be improperly aligned. The space the occupancy sensor has to cover is typically large, so small adjustments to sensor mounting may have large effects on coverage. Improper alignment of one sensor has a larger impact on useful energy savings when it is controlling many fixtures.
A maximum in useful energy savings corresponds to a good match in occupancy sensor coverage to illumination. If the occupancy sensor coverage is too large such that a controlled lamp does not contribute light to a large portion of the coverage zone, it may burn at full power when no one is using the light. If the sensor coverage is smaller than the contributed light of all controlled fixtures, the lights may not be triggered to full power reliably for the occupant.
In sum, conventional systems suffer from several shortcomings. The referenced shortcomings are not intended to be exhaustive, but rather are among many that tend to impair the effectiveness of previously known techniques concerning the control, and particularly dimming control, of lamps. Other noteworthy problems may also exist; however, those mentioned here are sufficient to demonstrate that methodology appearing in the art have not been altogether satisfactory and that a significant need exists for the techniques described and claimed herein.
In particular, a need exists for a modular lighting control system suitable for use with HID lamps that is easy to install, align, maintain, troubleshoot, and repair. More particularly, a need exists for easily retrofitting lamp fixtures that do not include a port suitable for use with a modular lamp controller.